Method for manufacturing acrylonitrile filaments

ABSTRACT

AN IMPROVED METHOD FOR MANUFACTURING ACRYLONITRILE FILAMENTS CONTAINING AT LEAST 85% BY WEIGHT OF ACRYLONITRILE BY SPINNING FILAMENTS, APPLYING SECONDARY STRETCHING UPON THE PRIMARILY STRETCHED FILAMENTS WHILE HEATING, APPLYING PREHEATING UPON THE SECONDARY STRETCHED FILAMENTS AND FINALLY, APPLYING ADDITIONAL HEAT TREATMENT UPON THE FILAMENTS. THE HEATING TEMPERATURE IN ALL HEAT TREATMENTS SHOULD BE CONTROLLED TO A PREDETERMINED RELATION. THE FILAMENTS MANUFACTURED ARE PLROVIDED WITH LESS UNEVENNESS OF THICKNESS, UNIFORM DYEABILITY, EXCELLENT CONFORMITY TO DYEING, AND IMPROVED MECHANICAL PROPERTIES. SO-CALLED DRY-WET SPINNING METHOD IS PARTICULARLY FAVORABLE FOR OBTAINING THE FILAMENTS IN THE PRESENT INVENTION.   D R A W I N G

9 7 YOSHIJIRO TABARA ETAL 3558576! METHCD FOR MANUFACTURINGACRYLONITRILE FILAMENTS Filed March 27. 1968 {Sheets-Sheet} 26, 1971YOSHIJIRO TABARA ETAL 3,558,761

METHOD FOR MANUFACTURING ACRYLONITRILE FILAMENTS 3 Sheet s-Sheet 3 FiledMarch 27, 1968 0mm Z IOF m2; OZFQwI zoozo HEATING TEMPERATURE IN CUnited States Patent Olfic 3,558,761 Patented Jan. 26, 1971 3,558,761METHOD FOR MANUFACTURING ACRYLONITRILE FILAMENTS Yoshi rro Tabara,Nobuhide Teranishi, Shigern Kikuchi, Kunito Ono, and Shoji Irnao,Otake-shi, Japan, as signers to Mitsubishi Rayon (10., Ltd. andMitsubishi Vonnel (30., Ltd., both of Tokyo, Japan, both companies ofJapan Filed Mar. 27, 1968, Ser. No. 716,382 Int. Cl. Dlllf 7/00 US. Cl.264-182 6 Claims ABSTRACT OF THE DISCLOSURE An improved method formanufacturing acrylonitrile filaments containing at least 85% by weightof acrylonitrile by spinning filaments, applying secondary stretchingupon the primarily stretched filaments while heating, applyingpreheating upon the secondary stretched filaments and, finally, applyingadditional heat treatment upon the filaments. The heating temperature inall heat treatments should be controlled to a predetermined relation.

The filaments manufactured are provided with less unevenness ofthickness, uniform dyeability, excellent conformity to dyeing, andimproved mechanical properties. So-called dry-wet spinning method isparticularly favorable for obtaining the filaments in the presentinvention.

The present invention relates to an improved method for manufacturingacrylonitrile filaments having improved qualities, more particularlyrelates to an improved method for manufacturing acrylonitrile filamentshaving less unevenness of thickness, uniform dyeability and excellentdyeability by, spinning filaments by any one of the known spinningmethods, primarily stretching the filaments at a stretching ratio offrom 2.00 to 7.00 applying secondary stretching upon the primarilystretched filaments while heating, applying preheating treatment uponthe secondarily stretched filaments, and finally, applying additionalheat treatment upon the preheated filaments.

In the present invention, acrylonitrile polymer containing at least 85%by weight of acrylonitrile is used as the material of the filaments ofthe present invention.

The principal object of the present invention is to provide a novelmethod for manufacturing acrylonitrile filaments having less unevennessof thickness together with silk-like luster.

The other object of the present invention is to provide an improvedmethod for manufacturing acrylonitrile filaments provided with uniformand excellent dyeability together with improved mechanical propertiessuch as tenacity, anti-frictional property and resistance against impactloading.

A further object of the present invention is to provide an improvedmethod for manufacturing acrylonitrile filaments which is provided withpreferable functional features as a material of textile products withless troubles in textile processing such as filament or yarn breakage.

In order to attain the above-described objects of the invention, themethod of the present invention comprises, spinning filaments by any oneof the known spinning methods, primarily stretching the filamentsapplying secondary stretching upon the primarily stretched filamentswhile heating them at a temperature (T between 170 and 220 C., applyingpreheating treatment upon the secondarily stretched filaments at atemperature between 80 C. and C. above the heating temperature (T in thesecondary stretching and, finally, applying additional heat treatmentupon the preheated filaments at a temperature between 230 and 250 C.under such a tension that the filaments are not shrunk more than 35%.

Further features and advantages of the present invention will beapparent from the ensuing descriptions with reference to theaccompanying drawings in which;

FIG. 1 is a schematic side view of a dry-wet spinning process favorablyused for the purpose of the present invention,

FIG. 2 is a schematic side view of a process for carrying out theadditional heating of filaments using a contacttype heating device,

FIG. 3 is a schematic side view of a process for carrying out theadditional heating of filaments using an indirect-type heating device,

FIG. 4 is a graphical drawing for showing the relation between heatingtemperature in the secondary stretching and the maximum shrinkage of thefilaments for various preheating temperatures,

FIG. 5 is a graphical drawing for showing the range of the combinationof the preheating temperature with the heating temperature in thesecondary stretching which is recommended for the purpose of the presentinvention,

FIG. 6 is a graphical drawing for showing the relation between theadditional heating temperature and tenacity of the filaments obtainedfor various heat shrinkages,

FIG. 7 is a graphical drawing for showing the relation between theadditional heating temperature and the saturated basic dye absorptionfor various heat shrinkages,

FIG. 8 is a graphical drawing for showing the relation between thetemperature and the time in additional heat treatment.

In the spinning of the filaments used in the present invention, thespinning solution is prepared by dissolving the before-mentionedacrylonitrile polymer with solvent such as dimethylformamide,dimethylacetamide or dimethylsulfoxide. Spinning of the filaments fromsuch a polymer solution can be carried out by any one of the knownspinning methods such as dry-spinning process, wet-spinning process ordry-wet spinning process. Among these spinning methods, the dry-wetspinning process is preferably employed in the manufacture of filamentsof the present invention in accordance with the beforementioned objectsof the present invention. Filaments thus formed are subjected to primarystretching and aftertreatment by the conventional procedure.

Referring to FIG. 1, an embodiment of the dry-wet spinning process isshown. In the present embodiment, a coagulating bath 2 is positioned 5to 15 mm. below the outlet of a spinning nozzle 1. The temperature ofthe coagulating bath 2 is maintained between 0 and 45 C. and the bathcontains from 30 to by weight of the solvent which is the same as thatused for dissolving the acrylonitrile polymer. It is recommended that astretch from 1.03 to 4.80 be applied to the filaments within an areabetween the spinning nozzle 1 and the first godet roller 3 in order toprovide the filaments having excellent luster and touch. Then thefilaments are primarily stretched in'a boiling water bath 5 positionedbetween the first godet roller 3 and the second godet roller 4. Whilethe stretching ratio of this primary stretching should be determined inaccordance with that of the later-mentioned secondary stretching, it isrecommended that the filaments be stretched in the boiling water at astretching ratio from 2.00 to 7.00 in order not to cause unevenness ofthe filaments obtained. After the primary stretching, the filaments arewashed in a washing bath 6, subjected to oiling treatment by an oilingdevice 7, dried by a drying roller 8 and taken up onto a package 9 by apackage drive 10.

As for the dry-spinning process, no special limitation of the spinningconditions is necessary. However, it is desirable to make the content ofthe residual solvent within the filaments before secondary stretchinglower than 2% by weight. In case this content of the residual solventexceeds 2%, it is liable to cause undesirable troubles in the followingheat treatments such as spot melting within the filaments or tinting ofthe filaments obtained.

Generally, the primarily stretched filaments obtained by theabove-described method is provided with tenacity from 1.6 to 2.5g./denier, elongation from 20 to 40% and shrinkage in boiling water fromto 18%. However, such primarily stretched filaments are not suitable fortextile products practically because of its poor antifrictionalresistance and poor dyeing property. Consequently, it becomes necessaryto apply a secondary stretching upon the primarily stretched filamentsin order to make the filaments suitable for actual utilization byimproving its fiber properties.

In the method of the present invention, a secondary stretching isapplied to the primarily stretched filaments while heating the filamentsusing such heating members as a heated roller, a heated pin, a heatedplate or a heated cylinder.

With respect to the heating temperature (T of the filaments in thesecondary stretching, it should be within the range of 170 and 220 C. Asan example of the effect of the heating temperature, the fiberproperties of the filaments obtained by secondarily stretching thefilaments, which are manufactured in such a manner as is detaillydescribed later in Example 1, at a stretching ratio of 2.5 at 160 to 235C., are illustrated in Table 1 for various secondarily stretchingtemperatures (T ranging between 160 and 235 C.

As is clearly shown in the table, a secondary stretching temperaturebelow 170 C. results in lowering of the dry tenacity, the dry elongationand the dry knot tenacity of the filaments obtained. This is because ofthe fact that the fiber structure of the primarily stretched filamentsis destroyed by secondary stretching them at such a low temperature. Onthe other hand, in case the secondary stretching temperature is higherthan 220 C., lowering of the tenacity of the filaments obtained is alsoobserved. This is due to the fact that the formation of fiber structureis difficultly occurred by secondarily stretching the filaments at sucha high temperature and effective stretching can not be performed.However, the filaments obtained by secondary stretching of the primarilystretched filaments at the above defined temperature are high in boilingwater shrinkage and insufiicient in dyeability and fiber properties.

against impact loading. When the filaments are not sufficiently providedwith such properties, they often cause many processing troubles such asfilament breakage during textile processing or yarn breakage duringweaving, both resulting in remarkably lowered quality of the textileproducts obtained.

In order to effectively eliminate such troubles, it is recommended thatan additional heat treatment be applied to the secondarily stretchedfilaments at a temperature between 230 and 250 C. in a tensioned orslack state.

Referring to FIG. 2, an embodiment of a continuous process for carryingout the method of the present invention is shown. This process ischaracterized by using a contact-type heating member such as a heatedplate, a heated pin or a heated roller. This type of process isfavorably used in case the additional heat treatment is applied to thefilaments under a tension. In the present embodiment, primarilystretched filaments 11 are taken out from a supply package 12,secondarily stretched while being contacted to the surface of heatedplate 13, preheated by a roller-type heating member 14, subjected toadditional heat treatment while being contacted to the surface of aheated plate 15 positioned between the preheating member 14 and atake-up godet roller 16 and,

finally, taken up onto a take-up bobbin 17.

As is well-known acrylonitrile filaments are extremely sensitive tofluctuation of tension applied upon the filaments under a heatedcondition. A large fluctuation of the tension often causes unevenness ofthe thickness and dyeing afiinity of the filaments manufactured.Therefore, in case the acrylonitrile filaments are heated under aslacked condition, it is strongly recommended that the tension becontrolled in such a manner that the fluctuation of the tension shouldbe limited within a narrow range. When heating of the filaments under aslacked condition is carried out by the process shown in FIG. 2, a largedisturbance of the tension by a frictional force due to contact betweenthe heating member and the filaments passing at a high speed isunavoidable.

In order to avoid such defects due to frictional contact between theheating member and the filaments, another type of the process forcarrying out the method of the present invention is shown in FIG. 3. Themechanical arrangement of the present embodiment is almost the same asthat of the embodiment shown in FIG. 2 with the only exception that anindirect-type heating member 18 is used instead of the contact-typeheating member 15 of the preceding embodiment. The indirect-type heatingmember 18 can be made both in the form of a heated cylinder or a pair ofheated plates faced with a slight intervening distance as the filamentscan be passed.

As an example of the effect of the additional heating of the secondarilystretched filaments manufactured in such a manner as is detailly statedlater in Example 2, the unevenness of the thickness of the filaments,kind of heating member, heating temperatures, tension applied to thefilaments and shrinkage of the filaments in the additional heattreatment are illustrated in Table 2.

TABLE 2 Heating Uneven tempera- Tension Shrinkage ness in Heating memberture in C in g. in percent U percent A heated cylinder of cm. dia. 28014 0 1. 0 D 280 3 2.0 2. 3 260 10 0 2. 4 250 5 2.0 7. 3

Moreover, the above-described secondary stretching alone is not enoughto provide the filaments with sufficient antifrictional resistance andstrong resistance In the illustrated example, the unevenness ofthickness in U percent of the filaments denier/40 filaments) beforeadditional heat treatment was 1.8. The secondary stretching of thefilament was performed at a temperature of 190 C. and at a stretchingratio of 3.50. After the secondary stretching, the filaments werecontinuously heated by a preheating roller maintained at 180 C. and fedto the additional heating process at a speed of 200 meters/ min.

In order to obtain good results by the method of the present invention,it is necessary to set suitably the relation among the temperatures ofsecondary stretching, preheating and additional heating.

In FIG. 4, the effect of the secondary stretching temperature T upon themaximum shrinkage of the filament during the additional heating forvarious preheating temperature T is shown. In the drawing, the maximumshrinkage of the filament is taken on the ordinate and the secondarystretching temperature T is taken on the abscissa while the curvedesignated with a corresponds to a preheating temperature T of 80 C.,curve b to 100 C., curve to 150 C., curve d to 175 C. and curve e to 200C. In the example shown, the primarily stretchedfilaments (560 d./40ft.) were subjected to secondary stretching at a speed of 200meters/min. and a stretching ratio of 3.50. After the secondarystretching, the filaments were heated with a preheating roller andfurther heated while passing through a dry heated cylinder of 100 cm.effective length maintained at 280 C.

As is clearly understood from the results shown in the drawing, littleshrinkage of the filaments is observed in case the preheatingtemperature T is lower than 80 C. provided that the secondary stretchingtemperature T isdefined Within a range between 170 and 220 C.Consequently, the preheating temperature T is required to be higher than80 C. in order to obtain an effective shrinkage of the filaments and,the higher the preheating temperature T the larger is the shrinkage ofthe filaments. Again, it can easily be estimated from the results shownin the drawing that the maximum value of the shrinkage of the filamentfor a certain preheating temperature can be obtained when the preheatingtemperature T falls within a range between T C. and T +10 C. Fromabove-described discussions, it can be concluded that in order toperform additional heat treatment effectively, the preheatingtemperature T must be defined by the following equations in accordancewith the secondary stretching temperature T The range of the combinationof the preheating temperature T and the secondary heating temperature Tdefined by the above-described equations is shown by the hatched area inFIG. 5, wherein the former is taken on the ordinate and the atter istaken on the abscissa.

In order to provide the filaments obtained with preferable fiberproperties as a material for actual textile products, it is generallyrequired to shrink the secondarily stretched filaments lower than 35%,more preferably from 10 to 35 while heating them at a high temperature.As is well-known, acrylonitrile filaments have a tendency to be easilyfibrillated resulting in whitening of the textile products made of them.In order to prevent such unfavorable fibrillation of filaments, theabove-described heat shrinking treatment is especially required in caseof acrylonitrile filaments. The shrinkage of the filaments by thistreatment is generally required to be higher than 10% asalready-described, however, it can also be lower than 10% in case nospecial heat shrinking treatment is necessary such as, for instance, incase of the manufacture of high bulky filament yarns.

Referring to FIG. 6, the relation of the heating temperature andtenacity of the filaments for various degrees of shrinkages is shown. Inthe drawing, tenacity of the filaments obtained is taken on the ordinateand the heating temperature is taken on the abscissa while the curvedesignated with :1 corresponds to 0% heat shrinkage, the

curve b to 10% and the curve 0 to 35 The numerals in parenthesis at theplotted points show the length of time in second required for sufficientshrinkage of the stretched filaments predetermined degree at thecorresponding heating temperature. From this result, it is clearly shownthat the heating temperature exceeding 250 C. causes deterioration offiber structure of the filament resulting in lowering of tenacity of thefilaments manufactured.

Referring to FIG. 7, the relation of the heating temperature and thesaturated basic dye absorption of the filaments obtained for variousdegrees of shrinkages is shown. In the drawing, the saturated basic dyeabsorption of the filaments is taken on the ordinate and the heatingtemperature is taken on the abscissa while the curve designated by acorresponds to a heat shrinkage of 0%, the curve b to 10% and the curve0 to 35 As is clearly shown in the drawing, a heating temperature lowerthan 230 C. results in poor degree of dye absorption of the filamentsmanufactured.

The combined discussion of the results shown in FIG. 6 and FIG. 7 leadsus to the conclusion that the optimum heating temperature of theadditional heating is in the range between 230 and 250 C.

With respect to the length of the heating time, sufiicient heating timeis necessary in order to highly shrink the filaments as shown in FIG. 6.In order to cause a shrinkage of filaments from 10 to 35% at a heatingtemperature between 230 and 250 C., from 0.10 to 20.0 seconds of heatingtime is generally required. In case the heating time is not long enoughto cause shrinkage of the filaments shaking of the filaments taken upongodet roller 16 in FIG. 2 is caused, resulting in unstable heatshrinking treatment leading to increased unevenness of the filamentsmanufactured. Moreover, when the filaments are passed through theprocess shown in FIG. 3, shaking of the filaments cause them to contactthe inside wall of the heating member 18 and this often results inbreakage of the filaments by melting by heat. Consequently, the lengthof the heating time must be determined within the above-described regionin accordance with the required degree of shrinkage and the degree ofthe heating temperature. However, it should also be noted too that a toolong heating time causes tinting and fragility of the filamentsmanufactured. The relation between the heating temperature and thecorresponding heating time is graphically shown in FIG. 8, wherein thereation is presented by a hyperbola-shaped curve. In case thecombination of the temperature and the time deviates too much from thiscurve, it results in fragility or tinting of the filaments obtained asabove-described.

The following examples are illustrative of the present invention, butare not to be construed as limiting the same.

EXAMPLE 1 25% of spinning solution was prepared by dissolving anacrylonitrile copolymer composed of 91.3% by Weight of acrylonitrile and8.7% by Weight of vinyl acetate with dimethylacetamide. Specificviscosity of the copolymer measured in dimethylfo rmamide at 25 C. was0.15. The solution was extruded through a spinneret having 40 holes of0.15 mm. dia. each into air and then directed into a coagulating bathcontaining dimethylacetamide and water to make filaments (500 denier/40filaments).

After leaving the godet roller, the filaments were primarily stretchedat a stretching ratio of 1.90. In the arrangement of the spinneret andthe coagulating bath, an intervening distance of 5 mm. was formedbetween the face of the spinneret and surface of liquid of the coagulating bath in order to make the filaments pass through the air justafter being extruded from the spinneret.

Next the primarily stretched filaments were fed to a process shown inFIG. 2, wherein the filaments were secondarily stretched at atemperature of C. a stretching ratio of 2.50 and at a speed of 200meters/ min., preheated at 200 C. for 13 seconds and finally heated bycontacting with a heated plate which was maintained at 250 C. and has alength of 35 cm. While stretching in a tensioned state.

The unevenness of thickness of the filaments obtained (200 denier/40filament) was 2.1, and the filaments were provided with tenacity of 3.53g./d., elongation of 17.1% and shrinkage in boiling water of 3.1%.

Then a false-twisting treatment was applied to the filaments obtainedunder such conditions that the temperature was 180 C., the rotatingspeed of the falsetwist spindle was 110,000 rpm, the false twists numberwas 1650 turns/meter and the overfeeding ratio was 0. The treatmentcould be carried out smoothly without troubles such as yarn breakage ortwist slacking, and the filaments obtained were provided with anexcellent extensibility.

A knitted cloth made of the filament yarn thus obtained was dyed withbasic dyes, and the resulting knitted cloth was provided with uniformcolor effect, beautiful luster and preferable bulkiness.

EXAMPLE 2 Filaments (560 denier/4O filaments) were obtained by the samemethod as Example 1 from the same spining solution as in Example 1. Thenthe filaments were fed to a process shown in FIG. 3, wherein thefilaments were secondarily stretched at a temperature f 190 C., at astretching ratio of 3.50 and at a speed of 200 meters/ min. preheated at200 C. for 1.3 seconds and finally heated while passing through a heatedcylinder of 100 cm. length heated at 280 C. while being shrunk 20%. Theunevenness of thickness in U percent of the filaments (200 denier/40filaments) obtained was 1.7, and the filaments were provided withtenacity of 3.13 g./d., elongation of 25.4% and shrinkage in boilingwater of 1.2%.

Then a woven cloth of tufted weave having refined surface effect wasmade with the filaments thus manufactured. For the same of confirmationof the effect of the present invention, this Woven cloth was dyed withbasic dyes and the resulting color of the cloth was preferably uniform.

EXAMPLE 3 Filaments obtained by the same method as Example 1 weresecondarily stretched at a temperature of 205 C., at a stretching ratioof 2.50 and at a speed of 400 meters/ min., preheated at 210 C. for 0.65seconds and finally heated by contacting with a heated plate of 35 cm.length and maintained at 250 C., in a tensioned state. The filaments of200 denier obtained was composed of 40 filaments.

Then the filaments were subjected to a false-twisting treatment underthe same conditions as those in Example 1. The treatment could becarried out smoothly without any troubles such as yarn breakage ortwists slacking.

By dyeing a knitted cloth made of the filament yarns thus manufactured,almost the same effects a those in Example 1 was obtained.

EXAMPLE 4 25% spinning solution was prepared by dissolving anacrylonitrile copolymer composed of 91.3% by weight of acrylonitrile and8.7% by weight of vinyl acetate with dimethylformamide. Specificviscosity of the copolymer was 0.15. Then the spinning solution wasextruded through a spinneret having 40 holes of 0.15 mm. dia. each toform filaments by dry-spinning method. The unstretched filaments (500denier/ 40 filaments) thus formed were stretched 3.78 times between thespinneret and the take-up roll. The content of the residual formamidewithin the filaments was lowered from 13% to 0.4% by washing thefilaments with boiling water at 100 C. for about '60 seconds. Aftersecondary stretching, preheating and additional heating in a tensionedstate under the same conditions as'those in Example 1, the filamentsobtained were provided with an unevenness of thickness in U-percent of2.5.

Then the filaments were subjected to a false-twisting treatment in thesame manner as in Example 1 without any troubles such as yarn breakageor twists slacking. By dyeing a knitted cloth made of the filament yarnsthus obtained, the same results as in Example 1 Was obtained with theonly exception that the hand feeling of the cloth obtained was slightlyharder than that in Example 1.

While the invention has been described in conjunction with certainembodiments thereof, various modifications and changes may be madewithout departing from the spirit and scope of the invention.

What is claimed is:

1. A method of manufacturing acrylonitrile filaments comprising:providing primarily stretched acrylonitrile filaments composed of morethan 85% by weight of acrylonitrile and the remainder a monomercopolymerizable therewith; secondarily stretching said primarilystretched filaments while maintaining same at a temperature T within atemperature range of from 170-220 C.; heat treating said secondarilystretched filaments within a temperature range of from C. to 10 C. abovesaid temperature T and then further heat treating said secondarilystretched and heat-treated acrylonitrile filaments at a temperaturebetween 230 C. and 250 C. while maintaining same under sufficienttension to prevent shrinkage of said filaments in excess of 35%.

2. A method according to claim 1; wherein said providing step comprisesproviding acrylonitrile filaments composed of more than by weight ofacrylonitrile and the remainder a monomer copolymerizable therewith, andprimarily stretching said acrylonitrile filaments in boiling water at astretching ratio between 2.0 and 7.0.

3. A method according to claim 1; wherein said providing step comprisesproviding dry-Wet spun acrylonitrile filaments.

4. A method according to claim 1; wherein said providing step comprisesproviding Wet spun acrylonitrile filaments.

5. A method according to claim 1; wherein said providing step comprisesproviding dry spun acrylonitrile filaments having 'a residual solventcontent less than 2% by weight.

6. A method according to claim 1; wherein said further heat treatingstep comprises heat treating said secondarily stretched and heat-treatedacrylonitrile filaments for from 0.1 to 20.0 seconds.

References Cited UNITED STATES PATENTS 2,445,042 7/1948 Silverman8--l30.1 2,558,733 7/1951 Cresswell et a1 264182 2,988,419 6/1961 Walter264206X 3,052,512 9/1962 Kocay et al. 264210 3,088,793 5/1963 Kundsen etal. 264-206X 3,447,998 6/1969 Fitzgerald et al. 264210ZL FOREIGN PATENTS1,017,855 1/1966 Great Britain 264182 41/7,898 4/1966 Japan 264206 JAYH. WOO, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Dated 26'lnventot-(s) YOShijiI'O et a1 It is certir'ied that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the heading of the patent, column 1, lines 6 and 7, delei "andMitsubishi Vonnel Co. Ltd. both"; lines 7 and 8, del

"both companies" and insert "a company" Signed and sealed this 7th dayof December 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK ActingCommissioner of Pa

